We now show that for a band insulator, it is possible to relate \(Z_q\) ,
as defined in Eq. (REF ) to the generalized Bargmann
invariant of Eq. (REF ). We can follow the steps of
Resta [1]}, and introduce a system periodic in \(L\) , with
lattice constant taken to be unity. We will consider a system with
one filled band, but we will comment on the many-band generalization
below. The \(L\)  Bloch vectors in the reciprocal cell \([0,2\pi /L)\)  can
be labelled,
\(k_s = \frac{2 \pi }{L} s,s = 0,...,L-1,\) 
